1. Field of the Invention
This invention relates to triazinylphosphonic acids. More specifically, the invention relates to 2,4-diamino-1,3,5-triazinyl-6-phosphonic acid derivatives and their use in the preparation of self-extinguishing polymeric compositions based on thermoplastic polymers or polymers with elastomeric properties, especially olefinic polymers or copolymers, either alone or in combination with ammonium or amine phosphates and/or phosphonates.
2. Discussion of the Background
Various methods are known in the art for reducing or eliminating polymer combustibility. Some of these methods are based on the use of metal compounds, especially of antimony, bismuth or arsenic, in combination with partly halogenated thermally unstable organic compounds such as chlorinated paraffin waxes.
Other methods are based on the use of substances able to produce intumescence. Intumescent formulations generally consist of the polymer and at least three main additives, of which one is essentially phosphorated, its purpose being to form during combustion an impermeable semi-solid vitreous layer consisting essentially of polyphosphoric acid, and to activate the intumescence formation process, a second contains nitrogen for foaming purposes and the third contains carbon acting as a carbon donor for forming an insulating cellular layer (char) between the polymer and the flame.
Examples of intumescent formulations of this type are those described in the following patents: U.S. Pat. No. 3,810,862 (Phillips Petroleum Co.) based on melamine, pentaerythritol and ammonium polyphosphate, U.S. Pat. No. 4,727,102 (Vamp S.r.l.) based on melamine cyanurate, a hydroxyalkyl derivative of isocyanuric acid and ammonium polyphosphate, and published patent application WO 85/05626 (Plascoat U.K. Limited) based on various phosphorus and nitrogen compounds, and in particular a combination of melamine phosphate, pentaerythritol and ammonium polyphosphate.
In more recent formulations, in addition to the use of an organic or inorganic phosphorus compound, a nitrogen containing organic compound is used, generally an aminoplastic resin obtained by condensing urea, melamine or dicyandiamide with formaldehyde. Examples of formulations comprising two additives are described in U.S. Pat. No. 4,504,610 (Montedison S.p.A.) based on oligomeric derivatives of 1,3,5-triazine and ammonium polyphosphate, and European patent 14,463 (Montedison S.p.A.) based on organic compounds chosen from benzylguanamine and products of the reaction between aldehydes and various nitrogenated cyclic compounds, in particular benzylguanamine-formaldehyde copolymers, plus ammonium polyphosphate.
Self-extinguishing compositions can also be obtained by using single-component additives containing both nitrogen and phosphorus in the organic molecule, as described in U.S. Pat. No. 4,201,705 (Borg-Warner Corp.).
These intumescence retarding systems give the polymer containing them the property of forming a carbon residue following fire or the application of a flame. Retarding systems of this type have numerous advantages, including the absence of corrosion in the machines used to work the polymers, lower smoke emission than systems containing metal compounds and halogenated hydrocarbons, and in particular the possibility of achieving satisfactory flame retardant properties in the polymer with a smaller total quantity of additive and hence without excessive fall-off in the polymer mechanical properties.